?Influence of Aging on Pathogenic ?-Synuclein Strains and Transmission Mechanism? Project Summary: Besides ?-synuclein transmission mechanism, the role of distinct strains of ?-synuclein is compelling to be understood. Understanding the influence of aging on the pathogenesis of synucleinopathies, including Parkinson's disease (PD), PD with dementia (PDD), dementia with Lewy body (DLB) and multiple system atrophy (MSA), is crucial for developing more effective symptomatic therapies. In this K01 proposal, three specific aims are proposed for understanding the influence of aging: (1) To generate and characterize pathogenic strain-specific ?-syn from brain tissue/CSF of patients with PD/PDD/DLB/MSA to controls by the factor of aging longitudinally and cross-sectionally. (2) To understand the influence of age on distinct pathogenic ?-syn strains from PD/PDD/DLB/MSA in vitro and in vivo. (3) To uncover the transmission mechanism of age-related distinct pathogenic ?-synuclein. To achieve the 3 specific aims, 6 methods/steps are required: (i) Dr. Juan Troncoso and Dr. Liana Rosenthal will provide the training to candidate on handling human brain tissue/CSF. Drs. Ted and Valina Dawson, and Dr. Mark Mattson will train the candidate using the misfolded ?-synuclein in brain tissue/cerebrospinal fluid (CSF) as templates, and with protein misfolding cyclic amplification (PMCA) technique, to generate distinct ?-synuclein strains. (ii) Scanning tunneling microscopy (STM) will be applied for imaging molecular structures of distinct ?-synuclein strains and distinguish the differences, and the alternative training will be available from Dr. Chen Wang if the potential problems appear. (iii) Atomic force microscopy (AFM) will be applied for observing assembly morphologies of distinct ?-synuclein strains. Dr. Mingdong Dong will provide the training on studying nano-mechanical properties and dynamic growth features of distinct ?-synuclein strains. (iv) Electrophysiology study on firing experiment will be hands- on training from Dr. Antonello Bonci. This training study is to understand the intrinsic and synaptic properties affected by distinct ?-synuclein strains. (v) In vivo microscopy will be hands-on training from Dr. Da-Ting Lin. This training includes performing all necessary surgical procedure to insert gradient index (GRIN) lens into substantia nigra and two-photon microscopy. This study will allow candidate to study the dopamine neuronal circuit dysfunction affected by stereotaxically injected with distinct ?-synuclein strains in striatum region for evaluation the transmission. (vi) Lymphocyte-activation gene 3 (LAG3) has been identified as ?-synuclein preformed fibrils (PFF) receptor, so it is worth to explore whether LAG3 can mediate the transmission of distinct ?-synuclein strains. Above all, this project proposed is to develop an independent research laboratory equipped to understand the distinct strains of amyloid proteins on misfolded structures, the transmission and the toxicity in neurodegenerative disorders, and to develop a programmatic line of research by successfully competing for funding.